Question: $ {-2\cdot \left[ \begin{array}{cc} 1 \\ 2 \\ 3 \end{array} \right]=}$
Answer: The Strategy To multiply a matrix by a scalar, we multiply each term of the matrix by the scalar. Multiplying each term $ {\begin{aligned}-2\cdot \left[\begin{array}{rr} {1} \\ {2} \\ {3} \end{array}\right]&=\left[\begin{array}{rr} -2\cdot{1} \\ -2\cdot{2} \\ -2\cdot{3} \end{array}\right] \\\\&=\left[\begin{array}{rr} {-2} \\ {-4} \\ {-6} \end{array}\right]\end{aligned}}$ Summary $ {-2\cdot \left[ \begin{array}{cc} 1 \\ 2 \\ 3 \end{array} \right]=\left[ \begin{array}{cc} -2 \\ -4 \\ -6 \end{array} \right]}$